"Dementia" is an umbrella term covering an array of neurological diseases and conditions that develop when neurons in your brain die or cease to function normally. The death or malfunction of neurons causes changes in memory, behavior and ability to think.

Alzheimer's disease, which is the most serious form of dementia, eventually leads to the inability to carry out even the most basic of bodily functions, such as swallowing or walking. Alzheimer's is ultimately fatal, as conventional treatment options are few and limited in effectiveness.

Disturbingly, Alzheimer's has reached epidemic proportions, currently affecting an estimated 5.4 million Americans.1 In the next 20 years it is projected that Alzheimer's will affect 1 in 4 Americans, rivaling the current prevalence of obesity and diabetes and by 2050, Alzheimer's diagnoses are projected to triple.2,3

Already, more than half a million Americans die from the disease each year, making it the third leading cause of death in the U.S., right behind heart disease and cancer.4,5 Considering there's no known cure and so few treatments, prevention is key.

Top Environmental Risk Factors Identified

As with autism, it's quite reasonable to suspect that a variety of factors are at play, collectively contributing to the rapid rise in Alzheimer's prevalence.

Experts at the Edinburgh University's Alzheimer Scotland Dementia Research Centre have now compiled a list of top environmental risk factors thought to be contributing to the epidemic.6,7,8 As reported by BBC News:9

"Dementia is known to be associated with lifestyle factors such as high blood pressure in mid-life, smoking, diabetes, obesity, depression and low educational attainment, as well as genetic factors.

But the Edinburgh researchers said a third of dementia risk was unexplained, and they want to determine whether other issues are at play, including the environment."

Not surprisingly (if you've been paying attention to the research), vitamin D deficiency, air pollution and occupational pesticide exposure top this list. Living close to power lines also has "limited yet robust" evidence suggesting it may influence your susceptibility to dementia.

All Forms of Air Pollution Raise Your Dementia Risk

The risk factor with the most robust body of research behind it is air pollution. In fact, they couldn't find a single study that didn't show a link between exposure to air pollution and dementia. Particulate matter, nitric oxides, ozone and carbon monoxide have all been linked to an increased risk.

Aside from raising your risk for dementia, a recent World Health Organization (WHO) report10 on environmentally related deaths claim that 1 in 4 deaths worldwide are now related to living and working in a toxic environment — with air pollution being the greatest contributor to this risk. As noted by WHO Director-General, Dr. Margaret Chan:

"A healthy environment underpins a healthy population. If countries do not take actions to make environments where people live and work healthy, millions will continue to become ill and die too young."

During the World Health Assembly, held in May 2016, WHO vowed it "will propose a roadmap to increase the global response by the health sector to reduce the effects of air pollution."

Pollution, Diabetes and Dementia

American researchers have also warned that exposure to air pollution for as little as one or two months may be enough to increase your risk of diabetes — especially if you're obese.11

Diabetes, in turn, is a significant risk factor for Alzheimer's, doubling your chances of contracting this devastating form of dementia. Alzheimer's was even tentatively referred to as type 3 diabetes at one time.

Recent research has also confirmed that the greater an individual's insulin resistance, the less sugar they have in key parts of their brain, and these areas typically correspond to the areas affected by Alzheimer's.12,13

Needless to say, the most significant contributor to insulin resistance and type 2 diabetes is not pollution but rather your diet. More specifically, eating a diet that is excessively high in net carbohydrates (total carbs minus fiber) and too low in healthy fats, which I will discuss further below, can contribute to insulin resistance.

Sensible Sun Exposure Is Important for Brain Health

The Scottish Dementia Research Centre also noted there's a very clear link between vitamin D deficiency and dementia. Indeed, studies have shown vitamin D plays a critical role in brain health, immune function, gene expression and inflammation — all of which influence Alzheimer's.

In a 2014 study,14 considered to be the most robust study of its kind at the time, those who were severely deficient in vitamin D had a 125 percent higher risk of developing some form of dementia compared to those with normal levels. According to the authors:

"Our results confirm that vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer disease. This adds to the ongoing debate about the role of vitamin D in nonskeletal conditions."

The findings also suggest there's a threshold level of circulating vitamin D, below which your risk for dementia increases. This threshold was found to be right around 20 nanograms per milliliter (ng/ml) or 50 nanomoles per liter (nmol/L). Please recognize that higher levels are associated with better brain health.

Based on a broader view of the available science, 20 ng/ml is still far too low, as the bulk of the research suggests a healthy range is between 40 to 60 ng/ml, certainly no lower than 40 ng/ml. Sadly, a vast majority of people are severely deficient, in large part because they've been fooled into fearing sun exposure.

Researchers have previously estimated that half of the general population is at risk of vitamin D deficiency or insufficiency. Among seniors, that estimate reaches as high as 95 percent. This suggests vitamin D may be a very important factor for successful prevention among the general population.

Researchers also believe that optimal vitamin D levels boost levels of important brain chemicals, and protect brain cells by increasing the effectiveness of glial cells in nursing damaged neurons back to health.

Vitamin D may also exert some of its beneficial effects on your brain through its anti-inflammatory and immune-boosting properties, which are well established.

Heart and Brain Health Are Closely Linked

It may be helpful to remember that Alzheimer's shares many risk factors with heart disease.15 This includes smoking, alcohol use, diabetes, high fasting blood sugar levels, insulin resistance and obesity.16

Arterial stiffness (atherosclerosis) is associated with a hallmark process of Alzheimer's, namely the buildup of beta-amyloid plaque in your brain.

The American Heart Association (AHA) also warns there's a strong association between hypertension and brain diseases such as vascular cognitive impairment (loss of brain function caused by impaired blood flow to your brain) and dementia.17

In one clinical trial, test subjects who consumed high-fructose corn syrup (HFCS) developed higher risk factors for cardiovascular disease in just two weeks, demonstrating just how influential your diet can be on your heart and brain health in the long term.

Such findings dovetail nicely with the conclusions reached by neurologist Dr. David Perlmutter, author of "Grain Brain," and "Brain Maker," who has concluded that anything that promotes insulin resistance will ultimately also raise your risk of Alzheimer's.

Exercise Is Important for Alzheimer's Prevention

The good news is that lifestyle choices such as diet, exercise and sleep can have a significant impact on your risk. As previously noted by Dr. Richard Lipton of the Albert Einstein College of Medicine — where they study healthy aging — lifestyle changes "look more promising than the drug studies so far" when it comes to addressing neurodegenerative disorders such as Alzheimer's.18

Exercise, for example, has been shown to protect your brain from Alzheimer's and other dementias, and also improves quality of life if you've already been diagnosed.19 In one study,20 patients diagnosed with mild to moderate Alzheimer's who participated in a four-month-long supervised exercise program had significantly fewer neuropsychiatric symptoms associated with the disease (especially mental speed and attention) than the non-exercising control group.

Other studies21 have shown that aerobic exercise helps reduce tau levels in the brain. (Brain lesions known as tau tangles form when the protein tau collapses into twisted strands that ends up killing your brain cells.) According to co-author Laura Baker:

"These findings are important because they strongly suggest a potent lifestyle intervention such as aerobic exercise can impact Alzheimer's-related changes in the brain. No currently approved medication can rival these effects."

Cognitive function and memory22 can also be improved through regular exercise, and this effect is in part related to the effect exercise has on neurogenesis and the regrowth of brain cells. By targeting a gene pathway called brain-derived neurotrophic factor (BDNF), exercise actually promotes brain cell growth and connectivity.

In one year-long study, elderly individuals who exercised grew and expanded their brain's memory center by as much as 2 percent per year, where typically that center shrinks with age. It's also been suggested that exercise can trigger a change in the way the amyloid precursor protein is metabolized,23 thus slowing the onset and progression of Alzheimer's.

Exercise also increases levels of the protein PGC-1alpha. Research24 has shown that people with Alzheimer's have less of this protein in their brains, and that cells that contain more of the protein produce less of the toxic amyloid protein associated with Alzheimer's.

Eating for Brain Health

Reducing your net carbs and increasing healthy fat consumption are another important part of the equation, and my optimized nutrition plan can set you on the right path in that regard.

Research25 from the Mayo Clinic reveals that diets rich in carbohydrates are associated with an 89 percent increased risk for dementia while high-fat diets are associated with a 44 percent reduced risk. Perlmutter places most of his patients on a ketogenic, high-fat and low-net-carb diet that is gluten-free, along with prescribed exercise.

One of the easiest ways to optimize your diet is to make sure you're only eating real food. Avoid processed foods of all kinds, as they contain a number of ingredients harmful to your brain, including refined sugar, processed fructose, grains (particularly gluten), genetically engineered (GE) ingredients and pesticides like glyphosate (an herbicide thought to be worse than DDT, which has already been linked to Alzheimer's). Opting for organic produce will help you avoid toxic pesticides.

Also choose organic grass-fed meats and animal products, as animals raised in concentrated animal feeding operations (CAFOs) are routinely fed GE grains contaminated with pesticides, along with a variety of drugs. Some researchers have even suggested Alzheimer's may be a slow-acting form of mad cow disease, acquired by eating contaminated meats. It's a rather compelling theory, considering mad cow disease originated in the CAFO system, where herbivores are forced to eat animal parts.

To Protect Your Heart and Brain, Trade Sugar for Healthy Fats, and Other Helpful Tips

Ideally, keep your added sugar levels to a minimum and your total fructose below 25 grams per day, or as low as 15 grams per day if you already have insulin/leptin resistance or any related disorders.

Healthy fats to add to your diet include avocados, butter made from raw, grass-fed organic milk, organic pastured egg yolks, MCT oil, coconuts and coconut oil (coconut oil, and to an even greater degree MCT oil, show particular promise against Alzheimer's) and raw nuts such as pecans and macadamia, both of which have a near-ideal ratio of protein and healthy fats.

Avoid all trans fats or hydrogenated fats that have been modified in such a way to extend their longevity on the grocery store shelf. This includes margarine, vegetable oils and various butter-like spreads. It's also advisable to:

Avoid gluten. Research shows that your blood-brain barrier is negatively affected by gluten. Gluten also makes your gut more permeable, which allows proteins to get into your bloodstream where they sensitize your immune system and promote inflammation and autoimmunity, both of which play a role in the development of Alzheimer's.

Optimize your gut health by avoiding processed foods, antibiotics and antibacterial products, fluoridated and chlorinated water and by regularly eating traditionally fermented and cultured foods, along with a high-quality probiotic if needed.

Optimize your vitamin D. This is ideally done through sensible sun exposure, but as a last resort, vitamin D3 supplements are better than nothing. Just make sure you also increase your intake of vitamin K2 if you take an oral vitamin D supplement. As for dosage, the "right" dose is one that will keep your blood level between 40 and 60 ng/ml.

Improve your magnesium levels. Not only does magnesium work in tandem with vitamin D and K2, preliminary research also suggests higher levels of magnesium in the brain help decrease Alzheimer symptoms. Magnesium threonate is one of the few magnesium supplements that appears to be able to actually cross the blood brain barrier, making it my first choice.

Increase your intake of animal-based omega-3. I prefer krill oil to fish oil here, as krill oil also contains astaxanthin, which appears to be particularly beneficial for brain health.

Other Alzheimer's Prevention Strategies

Besides exercise and the key dietary instructions just mentioned, the following suggestions may also be helpful for the prevention of Alzheimer's disease:

✓ Fasting

Ketones are mobilized when you replace nonfiber carbs with healthy fats. Intermittent fasting is a powerful tool to jumpstart your body into remembering how to burn fat and repair the insulin/leptin resistance that is a primary contributing factor for Alzheimer's.

✓ A folate-rich diet

Vegetables are your best form of folate, and you'd be wise to eat plenty of fresh raw veggies every day. Avoid supplements like folic acid, which is the inferior synthetic version of folate.

✓ If you enjoy black coffee, keep the habit

While I would not encourage you to drink coffee if you're not already a coffee drinker, if you enjoy it, there's good news. Caffeine triggers the release of BDNF that activates brain stem cells to convert into new neurons, thereby improving your brain health.

In one study, people with mild cognitive impairment whose blood levels of caffeine were higher (due to coffee consumption) were less likely to progress to full-blown dementia compared to those who did not drink coffee.26 In another study, older women whose coffee consumption was above average had a lower risk of dementia.27

Dental amalgam fillings, which are 50 percent mercury by weight, are one of the major sources of heavy metal toxicity. However, you really should be healthy prior to having them removed. Once you have adjusted to following the diet described in my optimized nutrition plan, you can follow the mercury detox protocol and then find a biological dentist to have your amalgams removed.

Drugs that block acetylcholine, a nervous system neurotransmitter, have been shown to increase your risk of dementia. These drugs include certain nighttime pain relievers, antihistamines, sleep aids, certain antidepressants, medications to control incontinence and certain narcotic pain relievers.

Statin drugs are particularly problematic because they suppress the synthesis of cholesterol, deplete your brain of coenzyme Q10, vitamin K2 and neurotransmitter precursors, and prevent adequate delivery of essential fatty acids and fat-soluble antioxidants to your brain by inhibiting the production of the indispensable carrier biomolecule known as low-density lipoprotein (LDL).

✓ Get plenty of restorative sleep

Sleep is necessary for maintaining metabolic homeostasis in your brain. Wakefulness is associated with mitochondrial stress; without sufficient sleep, neuron degeneration sets in. While sleep problems are common in Alzheimer's patients, poor sleep may also be contributing to the disease by driving the buildup of amyloid plaques in your brain.

While you sleep, your brain flushes out waste materials, and if you don't sleep well, this natural detoxification and clean-out process will be severely hampered.

✓ Challenge your mind daily

Mental stimulation, especially learning something new, such as learning to play an instrument or a new language, is associated with a decreased risk of Alzheimer's. Researchers suspect that mental challenge helps to build up your brain, making it less susceptible to the lesions associated with Alzheimer's disease.

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